Magnetic retrieval catheters have been used for nonsurgical removal of magnetically attractable objects from a cavity, duct, or passageway of a patient. Such catheters have been used, for example, in removing magnetically attractable stents from the bladder through the urethra and in removing accidentally swallowed, magnetically attractable foreign objects such as disk-shaped batteries from the stomach through the esophagus.
When retrieving accidentally swallowed, foreign objects from the stomach, the weight, size, shape, and frictional resistance of the object cannot be accounted for in advance. These problems are heightened when dealing with a small child who has a narrower esophagus and smaller stomach than that of an adult. Accidentally swallowed, magnetically attractable objects range in size and shape from small disk-shaped batteries to large metallic game ball pieces, ball bearings, whistles, and closed pocket knives. Therefore, a magnetic retrieval catheter capable of retrieving large, heavy, or irregularly shaped magnetically attractable objects is preferred. To insure that the magnet of the retrieval catheter will maintain its attachment to a magnetically attractable object, the size and shape of the catheter magnet has been increased. However, large-sized magnets are difficult to ingest and increase the likelihood of trauma to the esophageal passageway.
One prior art retrieval catheter having a large-sized magnet for removing a magnetically attractable object from the stomach has a cylindrical 1.0.times.1.0 cm magnet within a stainless steel casing. The casing and magnet are attached to the distal end of a 0.3 cm nylon-reinforced polyethylene catheter. As a result, the casing presents an abrupt edge for causing trauma to the esophageal passageway when removing the casing and the attached object from the stomach.
Another problem in removing magnetically attractable objects, particularly prior to the use of rare-earth magnets, is that these objects frequently become dislodged from the magnet during attempted retrieval, especially in the upper esophagus. This has often necessitated the simultaneous use of a second catheter, such as a Foley catheter, with an inflated balloon positioned distally of the object for the removal thereof. The use of two catheters complicates the retrieval procedure. In addition, this complication is heightened in small children, which constitute the largest population of patients.
Still another solution in removing magnetically attractable objects from the stomach is the use of a small-sized rare-earth magnet at the distal end of the catheter to maximize the strength of the magnetic field. However, a problem with such rare-earth magnets is oxidation. These rare-earth magnets oxidize when exposed to corrosive environments such as stomach acid and tend to break apart when so exposed. Furthermore, rare-earth magnets such as samarium-cobalt exhibit magnetic fields of limited strength for removing large, heavy, or irregularly shaped magnetically attractable objects.